Nonwoven roll towel material and method of producing the same

ABSTRACT

A nonwoven roll towel material including a central layer of an open mesh crossed thread fabric comprising resilient warp threads extending in the machine direction,and substantially non-resilient fill threads extending in the transverse direction. The thread count is in the range of from about 1.5 to about 5 threads per inch in both directions. A multi-ply layer of cellulosic tissue is bonded to each of the opposite faces of the central layer, and the resulting composite material is heavily embossed. The preferred embossing technique comprises passing a web of the composite material through two or more embossing stations on the surface of a single embossing roll, and drawing the web away from the surface of the embossing roll between successive stations. This technique produces two more embossments repeated continuously along the length of the composite material and out of register with each other.

Dec. 4, 1973 e. D. THOMAS ErAL 3,776,797

NONWOVEN ROLL TOWEL MATERIAL AND METHOD OI PRODUCING THE SAME Original Filed Dec. 25, 1968 i f \f I I I I I I I I I I I I I I I I l I I I I I I l I I I I I I I I I I l I I I I I I I I I I I I I I I I I I I I I I I 1 I L Y J\ I Y k l v J k V M M Y J 6 6' 6' wx xn mer.

' d'Id/V raw/4w "7 9. J flair z 'fffflA/I/ United States Patent 3,776,797 NONWOVEN ROLL TOWEL MATERIAL AND METHOD OF PRODUCING THE SAME Gordon D. Thomas, Ncenah, and James Tyson Gresham, Appleton, Wis., assignors to Kimberly-Clark Corporation, Neenah, Wis. Original application Dec. 23, 1968, Ser. No. 786,270, now abandoned. Divided and this application May 24, 1971, Ser. No. 146,512

Int. Cl. 1531f 1/00 US. Cl. 156-220 '8 Claims ABSTRACT OF THE DISCLOSURE A nonwoven roll towel material including a central layer of an open mesh crossed thread fabric comprising resilient warp threads extending in the machine direction, and substantially non-resilient fill threads extending in the transverse direction. The thread count is in the range of from about 1.5 to about threads per inch in both directions. A multi-ply layer of cellulosic tissue is bonded to each of the opposite faces of the central layer, and the resulting composite material is heavily embossed. The preferred embossing technique comprises passing a web of the composite material through two or more embossing stations on the surface of a single embossing roll, and drawing the web away from the surface of the embossing roll between successive stations. This technique produces two or more embossments repeated continuously along the length of the composite material and out of register with each other.

This application is a divisional of our copending ap plication Ser. No. 786,270, filed Dec. 23, 1968, and now abandoned.

The present invention relates generally to roll towels of the type used in kitchens and the like and, more particularly, to an improved nonwoven roll towel material.

It is a primary object of the present invention to provide an improved nonwoven roll towel material having an improved combination of strength, softness, absorbency, and other desirable characteristics.

Another object of the invention is to provide an improved nonwoven roll towel material of the foregoing type which can be efficiently produced at a relatively low cost.

Still another object of the invention is to provide a method of producing an improved nonwoven roll towel material of the type described above.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings, in which:

FIG. 1 is a schematic plan view of a composite roll towel material embodying the invention, with fragments of successive layers broken away to show underlying layers of the composite material.

FIG. 2 is a partially schematic end elevation of an embossing method and apparatus used in the production of the composite roll towel material shown in FIG. 1; and

FIG. 3 is a schematic plan view of an embossed flexible web formed by the method and apparatus illustrated in FIG. 2.

While the invention is susceptible of various modifications and alternative forms, certain specific embodiments thereof have been shown by way of example in the drawings which will be described in detail herein. It should be understood, however, that it is not intended to limit the invention to the particular forms disclosed but, on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Referring now more particularly to the accompanying drawings, the invention is embodied in a roll towel material represented in FIG. 1, and including a central layer 10 of nonwoven fabric made of open mesh cross-laid and bonded threads. More particularly, the fabric layer 10 comprises a set of spaced warp threads 11 extending in the machine direction and a set of spaced fill threads 12 which extend across the warp threads 11 in the transverse direction. Since the fabric is nonwoven, the fill threads 21 are all on the same side of the warp threads 20, with the two sets of threads disposed in face-to-face relation to each other and adhesively bonded together where the threads of one set cross the threads of the other set. Nonwoven fabrics of this type are well known in the art, and may be made by any of several different known methods and apparatus, one example of which is described in US. Pat. No. 2,841,202 to H. W. I-Iirschy. The threads in each of the two cross-laid sets normally run parallel to each other and are uniformly spaced, but the fabric may be formed with the threads following nonparallel or irregular patterns if desired, as long as one set of threads is disposed entirely on the one side of the other set. It will be understood that the term threads is intended to include both monofilament and multifilament structures, although multifilament structures are generally preferred in nonwoven fabrics.

In accordance with one aspect of the present invention, the warp threads 11 are made of a resilient material, the fill threads 12 are made of a stretchable non-resilient material, and the fabric 10 has a relatively low thread count in the range of 1.5 to 5 threads per inch, preferably 2 to 3 threads per inch, in both directions. The resilient nature of the warp threads 11 enhances the yieldability of the material for bulk improvement, without destroying the thread strength, during the embossing operation to be described below. A particularly suitable warp thread is 40 denier high tenacity nylon, which is not only resilient, but also provides an optimum strength-cost characteristic.

It is critical in the present invention that the fill threads 12 be substantially non-resilient in the final product, in order to avoid shrinkage of the composite towel material in the transverse direction after the material is embossed for bulk improvement as described below. More particularly, it has been found that there is a certain amount of delayed recovery in resilient threads that causes the roll towel to shrink during storage so that the core on which the towel is wound protrudes beyond the end of the towel roll. Even where a resilient material is allowed to return or spring back toward its original shape between the embossing and winding operation, there is a sufficient amount of delayed recovery to cause core protrusion within about two weeks after winding. This core protrusion, even if it is only A?" or less, causes shelf stacking problems and is also undesirable from an aesthetic standpoint.

Of course, the fill threads 12 must be somewhat the threads exhibit substantially no resiliency in the final embossed product. Both the fill thread and warp threads should also have a relatively high wet strength since the final product is to be used as a towel. A particularly suitable material that possesses the particular combination of properties required for the fill threads 12 is denier rayon, although certain other materials such as polyesters and the like may be selected with similar properties. The preferred 125 denier rayon has a relatively low level of stretch (10-15%), a relatively low elastic limit which is' easily exceeded by the stresses applied to the threads during the embossing operation to render the threads substantially non-resilient, and a strength about equivalent to that of the 40 denier high tenacity nylon that is preferred for the warp threads.

Bonded to the opposite faces of the central layer of nonwoven fabric are two outside layers 13 and 14 of cellulosic tissue, with each layer 13 and 14 preferably comprising one to four plies of creped cellulosic tissue. In the preferred embodiment illustrated in the drawings, each layer 13 and 14 is formed of two plies 13a, 13b and 14a, 14b, respectively, of creped cellulosic tissue. The cellulosic tissue is preferably wet strength treated with a dry basis weight before creping of from about 5 to about 13 pounds per 2,880 square foot ream, a Frazier porosity between about 45 and about 100, a stretch between about and about 100%, and a crepe ratio before stretching and pressing of from about 1.1 to about 2.5 as it is creped off the dryer of the paper machine. The creped tissue is typically stretched and pressed after creping to reduce the original high crepe ratio to about 1.1 to 1.8 in order to produce a soft sheet such as is customarily used in the manufacture of facial tissue. A particularly preferred cellulosic tissue for use in the illustrative embodiment of the invention is a creped tissue having the following characteristics:

(1) Dry basis weight: 7.6 lbs./2880 sq. ft./ply.

(2) Frazier porosity: 60 and above (c.f.m. at /2 water pressure drop4 ply).

(3) Tensile strength: Machine Direction Dry-1100 i200 gms. (gms./3"/ply); Cross Direction Dry- 600:100 gms.

(4) Stretch: -35%.

The above tissue permits good ply attachment to be obtained with the non-woven fabric using two conventional silicone calender rolls. In general, the calendering pressure required increases for creped tissue of lower porosity, higher weight, and higher strength, and increased fluidity of the fill adhesive at the calender nip may also be desirable.

The bonding of the two layers 13 and 14 of cellulosic tissue to the central fabric layer 10 is effected by adhesive that is originally applied to only the fabric layer, in the illustrative embodiment. This adhesive is applied to both sets of threads 11 and 12 in order to achieve the most effective bonding of the warp and fill threads 11 and 12 to each other and to the tissue layers 13 and 14; the warp thread adhesive is primarily responsible for bonding the warp threads to the fill threads during production of the fabric layer 10, while the fill adhesive is primarily responsible for bonding the fill threads to the tissue layers 13 and 14 to prevent grinning (i.e., rupture of the tissue in the transverse direction before thread breakage). With the preferred materials described above, using two plies of cellulosic tissue on each side of the central fabric, the warp thread adhesive is applied at a rate of 1.2 to 1.5 gms./sq. yd., and the fill adhesive is applied at a rate of 4.0 to 6.0 gms./sq. yd. If a greater number of tissue plies are used, they may be interbonded by adhesive applied to a sufiicient area of adjacent surfaces of the multiple plies to hold them together during use; in this case, the adhesive should be applied in a discontinuous pattern so that the desired interbonding is achieved with a minimum of adhesive and without reducing the flexibility of the composite material. In any event, the particular adhesive or adhesives employed throughout the towel material should always be insoluble in water and any other liquids that might be absorbed in the towel during use.

While various adhesives may be employed, advantages reside in the use of plastisols which, as is well known, are colloidal dispersions of synthetic resins in a suitable organic ester plasticizer. While many adhesives of this nature are known, those found particularly useful for incorporation in the product of this invention include vinyl chloride polymers, and copolymers of vinyl chloride with 4 other vinyl resins, plasticized by organic phthalates, sebacates, or adipates. These combinations provide a fast curing plastisol adhesive characterized by relatively low viscosity, low migration tendencies, and minimum volatility. Such adhesives remain soft and flexible after curing, can be reactivated by the application of heat and pressure, such as by hot-calendering, and insure that the resultant laminated product retains the desired softness, and proper hand and feel. Although plastisols .are preferred, polyvinyl resins per se, plasticized or unplasticized, such as polyvinyl acetate, and copolymers may also be used. Other flexible adhesive may also be used, including acrylic resins such as the alkyl acrylates, and butadiene resins such as butadiene-styrene and butadiene acrylonitriles.

It has been found that the particular combination of materials embodied in the composite laminate of FIG. 1 is superbly suited for use as a roll towel, particularly when embossed by the procedure to be described below. Thus, when made with the preferred materials mentioned above and a 3 x 2.5 thread count (number of warp threads per inch x number of fill threads per inch) in the non-woven fabric 10, a composite roll towel was produced with the following characteristics:

(1) Tissue plies 4 As can be seen from the above test data, the improved roll towel provided by this invention exhibits improved strength, absorbency, bulk, and roll diameter, particularly when compared with other roll towels presently on the market. Moreover, the combination of the multiple plies of relatively light-weight cellulosic tissue and the reinforcing fabric provides improved tear strength, softness, and lirnpness and is more aesthetically pleasing for roll towel use.

To provide the composite material with the high bulk and texture desired in a roll towel, it is heavily embossed, preferably by the technique illustrated in FIGS. 2 and 3, so that a substantial portion of the cellulosic tissue in each of the multi-ply layers 13 and 14 protrudes through the windows of the open mesh fabric 10 and beyond the opposite face thereof. More particularly, a continuous web 20 of the previously formed flexible laminate is drawn around an inlet roller 21 and continuously advanced under a guide roll 21a into engagement with a driven embossing roll 22 at a first embossing station where the web is pressed firmly against the surface of the embossing roll to form a first embossment in the web. That is, the web 20 is drawn through the nip formed by the metal embossing roll 22 and a first rubber roll 23 so as to form a first series of repetitive embossments along the length of the web 20. As can be seen in FIG. 2, the guide roll 21a is located to feed the web 20 into the nip of the rolls 22 and 23 along a common tangent line for the two rolls. The embossments formed at this first embossing station are illustrated schematically in FIG. 3 as embossments A repeated continuously along the length of the web 20. The repetition rate of the embossments A" may be varied by a number of factors, including the diameter of the embossing roll 22 and the rate of repetition, if any, of the embossing pattern on the surface of the roll 22. For example, if the pattern of the embossing surface on the roll 22 repeats itself every ten inches around the circumference of the roll 22, then the length of each embossment A illustrated in FIG. 2 will also be ten inches, i.e.,

the embossments A will be repeated every ten inches continuously along the length of the web 20.

As the embossed web is continuously withdrawn from the first embossing station, it is drawn away from the surface of the embossing roll, and then passed through a second embossing station on the surface of the same embossing roll used to form the embossments at the first station. More particularly, the embossed web 20 is continuously withdrawn from the nip of the rolls 22 and 23 and drawn away from the surface of the embossing roll 22 over a guide roll 24a. From the guide roll 24a, the embossed web is returned to the surface of the driven embossing roll 22 over a second guide roll 24b, and passed through a second embossing station formed by the nip of the metal embossing roll 22 and a second rubber roll 25. As can be seen in FIG. 2, the second guide roll 24b is located to feed the web 20 into the nip of the rolls 22 and 25 on a common tangent line for the two rolls. As the web is passed through the nip of the rolls 22 and 25, it is again pressed firmly against the surface of the roll 22 to form a second embossment in the Web. These second embossments are illustrated schematically in FIG. 3 as embossments B repeated continuously along the length of the web 20, with the repetition rate being determined by the same factors discussed above in connection with the first embossments A.

It is preferred that the embossments formed at the second embossing station be out of register with the embossments formed at the first embossing station, so that the maximum area of the web is embossed, and to avoid overstressing any given portion of the web material. Consequently, if the embossing pattern on the surface of the metal roll 22 repeats itself around the circumference of the roll 22, the locations of the rubber rolls 23 and 25, the rate of advancement of the web 20, and the distance that the web 20 is drawn away from the surface of roll 22 by the guide rolls 24a and 24b must be selected so that the embossments formed at the successive embossing stations are out of register with each other. In one example of the illustrative apparatus, the embossing roll 22 has a diameter of 20 inches with an embossing pattern that repeats itself every ten inches around the circumference of the roll; the embossing roll 22 is driven at a rate suflicient to provide a Web speed of 500 feet per minute; the embossing stations are located at the angular positions shown in FIG. 1; and the centers of the guide rolls 24a and 24b are located 36 and 28 inches, respectively, from the center of the driven embossing roll 22.

It will be understood that any desired number of additional embossing stations may be provided around the circumference of the embossing roll 22, depending upon the characteristics desired in the final embossed web. Thus, in the illustrative system, a third embossing station is provided by a third rubber roll 26 bearing against the outer surface of the roll 22. As the double-embossed web 20 emerges from the nip of the second rubber roll 25 and the embossing roll 22, the web is drawn outwardly away from the surface of the embossing roll 22 and over a guide roll 27a. From the guide roll 27a the doubleembossed web is returned under a second guide roll 27b to the surface of the roll 22, and then passed through the third embossing station formed by the nip of the third rubber roll 26 and the metal embossing roll 22. As in the case of guide rolls 21a and 24b described previously, the second guide roll 27b is positioned so that the web 20 is fed into the nip of the rolls 26 and 22 on a common tangent line for the two rolls.

As the web is passed through the nip of the rolls 26 and 22, it is once again pressed firmly against the surface of the metal roll 22 to form a third embossment in the web. These third embossments are illustrated schematically in FIG. 2 as embossments C repeated continuously along the length of the web 20, with the repetition rate being determined by the same factors discussed above in connection with embossment A. It is again important that the embossments C be out of register with the embossments A and B, and in the particular example described previously the centers of the guide rolls 27a and 27b are located 63 and 32 inches, respectively, from the center of the embossing roll 22. The resulting triple-embossed Web emerging from the nip of the rolls 26 and 22 is withdrawn from the embossing machine as at 30 for winding or further processing.

In order to maintain the rubber rollers 23, 25 and 26 at a temperature sufficiently low to prevent degradation of the rubber, the rollers are preferably water cooled. In general, it is desirable to prevent the temperature from rising above about 200 F. at any point in the rubber, which is generally in the form of a cover on the outer surface of a hollow metal drum. To facilitate cooling, the rubber cover is typically made as thin and hard as possible, consisting with good embossing performance. As mentioned previously, it is important that the embossing pressure he sufiicient to stretch the fill threads 12 beyond their elastic limit so that the threads are permanently stressed, whereas the resilient warp threads 11 tend to spring back to their original dimensions and configuration as soon as the embossing pressure is released. Consequently, a substantially constant Web length is maintained between successive embossing stations. Without the resilient warp threads 11 extending continuously in the machine direction in the web, the web continuously acquires a permanent stretch at each embossing station, so that the web length between each pair of successive embossing stations gradually increases.

Thus, while it is important to provide non-resilient fill threads to avoid core protrusion, as described previously, it is equally important, when using the illustrative embossing technique, to provide resilient warp threads to prevent any permanent elongation of the laminated web at any given embossing station so that a substantially constant web length is maintained between successive embossing stations.

One of the significant advantages of the illustrative embossing technique is that the flexible web may be embossed to any desired degree by using a single embossing roll, and yet the embossing pressure required at each embossing station may be sufliciently low to provide a long operating life for the embossing equipment, particularly the rolls 23, 25 and 26 which are conventionally made of rubber, and which cooperate with the metal embossing roll to form the embossing stations. For example, if the same degree of embossing attainable with the threestation arrangement shown in FIG. 1 were to be achieved with a single embossing station, the embossing pressure required would be so great that the risk of failure of the rubber roll from heat build-up would render the operation unfeasible. Furthermore, supplemental operations such as pin embossing and the like are not necessary to improve the response of the flexible web to the main embossing operation, because the desired yieldability, bulk, and embossing response is improved in each subsequent embossing station, and it is simply a matter of providing the necessary number of such stations around the single embossing roll.

As the toweling is wound on cores after withdrawal from the embossing machine at 30, transverse tear lines are formed by repetitively perforating the toweling at suitable intervals with knives which are closely enough spaced to at least partially cut substantially all the warp threads. For example, the toweling may be perforated every 11 inches with knives having cutting areas separated by 0.010" spaces, to form corresponding bonds in the toweling. With the exemplary thread counts mentioned previously, the 0.010 bonds eliminate completely uncut warp threads or thread hang-ups which cause poor dispensing from the roll during use. To prevent loose cores due to shock absorption during handling or shipment, the toweling is preferably wound on cores having a semi-permanent or a permanently dry bond pick-up adhesive on the surface thereof.

We claim as our invention:

1. A method of producing a nonwoven roll towel material, said method comprising the steps of providing web of nonwoven fabric made of open-mesh, cross-laid and bonded threads including stretchable and resilient warp threads spaced from one another and extending in the machine direction and stretchable fill threads spaced from one another and extending in the transverse direction, said nonwoven fabric having a thread count of from about 1.5 to about threads per inch in both the machine and transverse directions, bonding to each of the opposite faces of said web of nonwoven fabric a layer of cellulosic tissue, and heavily embossing the resulting web of composite material formed by said fabric layer and said cellulosic tissue layers with the embossing pressure being sufficient to stretch said fill threads beyond the elastic limit thereof so as to render said fill threads substantially nonresilient.

2. A method of producing a nonwoven roll towel material as set forth in claim 1 wherein said web of composite material is embossed by passing the web through two or more embossing stations spaced around a single embossing roll, and drawing the web away from the surface of said embossing roll between each pair of successive embossing stations so that the repetitive embossments formed in said web at successive embossing stations are out of register with each other.

3. A method of producing a non-woven roll towel material as set forth in claim 1 wherein said web of composite material is embossed by continuously advancing the web into engagement with the single embossing roll at a first embossing station where the web is pressed firmly against the surface of said embossing roll to form a first embossment in the web, continuously withdrawing the embossed web from said first embossing station and drawing the web away from the surface of said embossing roll, and continuously returning the embossed web to the surface of said single embossing roll and into engagement with said roll at a second embossing station where the web is again pressed firmly against the surface of said roll to form a second embossment in the web, said second embossment being out of register with said first embossment.

4. A method of producing a nonwoven roll towel material as set forth in claim 1 wherein said web of composite material is embossed by passing the web through two or more embossing stations spaced around a single embossing roll with the web being pressed against the surface of said roll at each of said stations to form embossments in the web, drawing the web away from the surface of said embossing roll after each embossing station and then returning the web to the surface of the embossing roll at the next embossing station so that the repetitive embossments formed in said web at successive embossing stations are out of register with each other.

5. A method of producing a nonwoven roll towel material as set forth in claim 1 wherein said web of composite material is embossed so that a substantial portion of the cellulosic tissue in each of said layers protrudes through said open-mesh fabric and beyond the opposite face thereof, and including the step of winding the final embossed material on a core, the substantially non-resilient fill threads stabilizing the transverse dimension of the embossed material to prevent transverse shrinkage of the material wound on said core and resulting core protrusion.

6. A method of producing a nonwoven roll towel material as set forth in claim 1 wherein said warp threads comprise high tenacity nylon threads of about 40 denier.

7. A method of producing a nonwoven roll towel material as set forth in claim 1 wherein said fill threads comprise rayon threads of about 125 denier.

8. A method of producing a nonwoven roll towel material as set forth in claim 1 wherein each of said layers of cellulosic tissue comprises 1 to 4 plies of cellulosic tissue having a dry basis weight between about 5 and about 13 pounds per 2880 square feet, a Frazier porosity between about 45 and about 100, and a stretch between about 20% and about References Cited UNITED STATES PATENTS 3,611,919 10/1971 Thomas 10123 3,188,948 6/1965 Fischer et al. 101l78 2,841,080 7/1958 Viscardi 101l78 3,546,056 12/1970 Thomas l61-133 2,902,395 9/1959 Hirschy et al. 16182 GEORGE F. LESMES, Primary Examiner I. J. BELL, Assistant Examiner US. Cl. X.R. 

